The term "flexible graphite" as used herein represents the exfoliated reaction product of rapidly heated graphite particles which have been treated with an agent that intercalates into the crystal-structure of the graphite to expand the particles at least 80 or more times in the direction perpendicular to the carbon layers in the crystal structure. Flexible graphite and the making thereof is described in U.S. Pat. No. 3,404,061 Shane et al. Flexible graphite may be compressed into thin sheets (hereinafter referred as "foil") with a density approaching theoretical density, although a density of about 50 to 85 lbs./ft..sup.3 is suitable for most applications, including compression into shapes suitable as seal rings in engine exhaust applications.
Flexible graphite foil is coherent, with good handling strength, and flexible graphite foil can be wound into rolls and can also be wrapped around metal fixtures such as mandrels, possesses heat insulating properties and is, accordingly, particularly useful for high temperature applications such as engine exhaust seal ring applications, particularly when formed in a composite with metal mesh.
Prior art flexible graphite-metal mesh composites have been found to be effective in seal ring applications but have been characterized by "squeaky" operation, i.e. the emanation of audible responses, which suggest that there is an imminent failure situation, although there is no known data to support a relationship between the audible emanations and failure and no such failures have been detected. Since the suspicion of failure remains, however, even though unsubstantiated, it is important to eliminate the audible emanations so that a flexible graphite-metal composite seal ring will become more acceptable to users.
Accordingly, it is an object of the present invention to provide a flexible graphite-metal composite seal ring for engine exhaust systems which does not generate audible responses during use. Other objects will be apparent from the following description and claims taken in conjunction with the drawing.